Wobble knife drives have been used on agricultural harvesters for a number of years. Many manufacturers use them on combine harvesters. As the capacity of combine harvesters has increased over the years, the width of swath harvested has increased. Today it is common to find harvester headers which sever a swath of crop material thirty feet wide during each pass through a field.
The force required to reciprocate a knife cutting a thirty foot swath of crop material can be large. This is especially true in crops with a tough or hard stalk, and in crops that are growing with weeds. The vibrations induced in a knife drive on a large header when cutting a tough crop can cause drive failures.
A reciprocating knife driven by a wobble knife drive with a modified centrifugal pendulum vibration absorber is currently available on combine harvesters. This vibration absorber is substantially identical to bifilartype centrifugal pendulum vibration absorbers used on some diesel engine crankshafts and shown in engineering books on vibration theory.
The bifilar-type centrifugal vibration absorbers work well on harvester knife drives. They absorb vibration and reduce wear and failures in the knife drive. However, there are problems. The vibration absorbers have a number of parts subject to wear. The overall width of a header with a bifilar-type centrifugal vibration absorber is increased. During an overload of the commercially available vibration absorber, the U-shaped weights strike the support disk or plate making objectionable noise and occasionally damaging the machine.